Increasing numbers of all-electric vehicles are being used, notably in urban areas. The use of electric vehicles yields numerous advantages. The batteries are critical components of these types of vehicle. More generally, the management of energy for these vehicles is a completely different problem from that of thermal vehicles running on fossil energy.
In particular, batteries fitted in electric vehicles have a finite energy capacity. Moreover, the electrical recharging of a battery takes a very long time. Therefore it is essential for the driver of a vehicle of this type to be certain that the amount of energy stored in the batteries is sufficient to cover a desired route while activating the auxiliary equipment for providing passenger comfort.
For vehicles with combustion engines, the question of managing auxiliary equipment (heating, air conditioning, and the like) does not arise, because fossil energy is available on road networks at numerous rest stops. Thus the strategy for managing the auxiliaries is reduced to satisfying the driver's requests. In the case of electric vehicles, it may rapidly become impossible to use this simple strategy. Storage capacity is limited and recharging facilities are lacking at the present time. If requests for comfort are met at all costs (using the heating, car radio, and other auxiliary equipment), the energy resources of the battery may be rapidly exhausted. This may adversely affect the purpose of the mission, which is to arrive at the route destination.
If an energy management strategy is implemented to minimize energy consumption, meet the constraint of reaching the destination, and satisfy requests for comfort, it may become constraining for the driver. This is because these criteria may impose a very slow driving style and fail to meet the driver's requests in terms of speed.
Numerous articles describe solutions for implementing energy management systems in hybrid, combustion engine and electric vehicles. These systems are also referred to as EMS, an acronym for the English expression “Energy Management Systems”. The term EMS may be used subsequently.
As a general rule, these articles describe energy management strategies having the aim of finding the best scenario for activating the combustion engine and/or electric motor at a given instant, on the basis of criteria relating to the consumption and/or pollution emission of a vehicle. Where purely electric propulsion is used, these strategies cannot provide simultaneous management of the comfort requirements of vehicles, notably requests for auxiliary equipment, the power consumption of the battery, and the performance specifications of vehicles such as the journey time.
In the field of energy management for purely electrically propelled vehicles, patent application EP1462300 A1 may be cited. In this document, the aim is to enable the driver to manage the battery charging and discharging level, using certain information supplied to the vehicle driver. A drawback of the proposed solution is that it requires the use of a battery charger, which is a major constraint.
These prior art solutions, therefore, do not resolve the problem encountered by drivers, notably drivers of all-electric vehicles. This is because the driver needs, above all, to be certain that the amount of energy stored in the batteries is sufficient to cover the route. If the amount of energy is insufficient to provide reliable assurance that the destination will be reached, the driver must be offered a driving style which will enable him to reach the destination. This objective must be met, regardless of the identity of the vehicle driver. Furthermore, since the maximum storage capacity of present-day batteries is still far too low, care must be taken to avoid wastage, in order to minimize energy consumption.